Sunday 23 May 2021

Helarctos malayanus: Understanding the impact of Palm Oil plantations around the Tabin Wildlife Reserve on Malayan Sun Bears

Wildlife reserves around the world are coming under increasing pressure due to rising Humans populations and activities in adjacent areas. Originally conceived as refuges in which the core habitats of threatened species would be preserved, surrounded by buffers of limited activity, many of these reserves now have intensive Human activities extending directly to their boundaries, provoking a rise in Human-wildlife activities, both as Humans enter parks to hunt or extract Plant or mineral resources, and as Animals on the boundaries of parks try to take advantage of Human resources, by crop raiding or hunting livestock.

Populations of Animals in parks are therefore becoming particularly prone to edge effects, with Animals populations living close to reserve boundaries particularly prone to extinction. This is particularly true for Animals living on smaller reserves, and large carnivorous Animals, which require larger territories and are more vulnerable to Human-wildlife contacts.

Wildlife in Southeast Asia is increasingly vulnerable to a range of anthropogenic threats, driven largely by deforestation. More than 50% of tropical forests in Southeast Asia have been felled for agriculture and other commercial purposes. As well as the direct loss of habitat, many wildlife populations have become more vulnerable to hunting, as new road networks open up formerly remote areas. This hunting is driven both by the desire to obtain bushmeat for local consumption, and the international wildlife trade, in which both whole Animals and Animal body parts are traded over long distances across international boundaries.

Sun Bears, Helarctos malayanus, are hunted for their paws and gall bladders, which have high commercial values on the international market. The species is found in the evergreen forests of the Sundaland sub-region and the seasonal forests of mainland Southeast Asia. Sun Bears are currently classified as Vulnerable under the terms of the International Union for the Conservation of Nature’s Red List of Threatened Species, but their populations are thought to have declined by 30% in the last 30 years, due to a combination of habitat loss and hunting for body parts, making it likely the species will be reclassified as Endangered in the near future.

A Borneo Sun Bear, Helarctos malayanus euryspilus, in Sabah State, Malaysia. Sunbear Survival.

Efforts to set up conservation plans for Sun Bears have been hampered by a lack of information about their distribution, ecology, and population structures, and while some work to improve our understanding of this has been undertaken in recent years, there is still much about the species that is not fully understood. Notably, it was long thought that Sun Bears were restricted to undisturbed primary rainforests, but recent studies have suggested that they are also found to some extent in secondary forests and even areas that have recently been cleared by loggers.

The impact of land-use changes upon vulnerable species has been little studied in Southeast Asia, although, as in other areas, these impacts are likely to be severe when they are close to reserve boundaries, as such encroachments will lead to increased Human-wildlife conflicts, enhanced opportunities for poachers to target wildlife, barriers to the movement of species between remaining areas of habitat, and changes in Animal behaviour in changing environments. In Malaysia there has been a rapid spread of monocultural Oil Palm plantations into many areas previously covered by pristine rainforests, with a subsequent negative impact on wildlife populations. There plantations have a severe impact on Mammal diversity, with the number of species declining rapidly away from areas of natural forests. Nonetheless, many species have found ways to exploit these new environments, and Sub Bears, which are generally diurnal, are known to make nocturnal foraging forays into Oil Palm plantations. Such crop-raiding behaviour gives the Bears access to a highly nutritious food-source, but fuels conflict with villagers and plantation workers. This in turn tends to lead to a rise in poaching, typically by snaring, which leads to boundary areas becoming population sinks, as Bears in these areas are drawn into the plantations to access the new food source, where they become more vulnerable to poaching.

In a paper published in the journal Wildlife Biology on 3 May 2021, Thye Lim Tee of the Department of Biological Sciences at Sunway University, Frank van Manen of the Interagency Grizzly Bear Study Team at the Northern Rocky Mountain Science Center, Petra Kretzschmar of the Department of Evolutionary Ecology at the Leibniz Institute for Zoo and Wildlife Research, Stuart Sharp of the Lancaster Environment Centre at Lancaster University, Siew Te Wong of the Bornean Sun Bear Conservation Centre, Sumbin Gadas of the Sabah Wildlife Department, and Shyamala Ratnayeke, also of the Department of Biological Sciences at Sunway University, present the results of a study which used remote cameras along a gradient across the boundary of the Tabin Wildlife Reserve in Sabah State, Malaysian Borneo, to determine the presence or absence of Sun Bears in landscapes subject to Human alteration.

The Tabin Wildlife Reserve is an area of lowland Dipterocarp rainforest northeast of Lahad Datu. It was created in 1984 for the conservation of the Sumatran Rhinoceros, Dicerorhinus sumatrensis, and now represents the largest contiguous forested area in Sabah, although it is surrounded by Oil Palm plantations. Rainfall in the reserve averages 150–300 cm per year, and temperatures from a mean daily maximum of 32.0°C to a mean daily minimum of 22.0°C.

The Tabin Wildlife Reserve preserves an excellent habitat for forest-dwelling Bornean species, but Oil Palm plantations now extend to its boundaries on almost all sides. Google Maps.

Tee et al. used data from two sources in their study; the first was collected during Sumatran Rhino surveys at Tabin Wildlife Reserve from July 2012 through February 2013, and the second carried out by Thye Lim Tee April–October 2017. Only data from independent camera sites that were located at least 1 km apart was used in the study, with sites that were closer being omitted, resulting in a total of 83 camera sites being included in the study. 

The 2012-13 Rhino surveys were conducted in the central and northern part of Tabin Wildlife Reserve, with cameras placed within 6 km² square grid cells based on a minimum home-range size of Sumatran Rhinos at game trails, mud wallows or hill crests. This study yielded data from 39 cameras with an average distance of 1.7 km. These camaras operated 24 hours a day for an average of 96 days.

During the 2017 study 44 passive infrared remote cameras were deployed along forest trails, the reserve boundary, old logging roads and within the core area of the reserve. These cameras were separated by an average distance of 1.4 km, selected to establish a gradient in relation to landscape features of interest, such as distance to roads and reserve boundary, with cameras placed to optimise Sun Bear detection, and baited with Shrimp paste and pieces of salted Fish placed in black shading net. These cameras were deployed at each site for 28 days, before being moved to a new site, with 13-18 cameras active at any one time.

Tee et al. used a linear model to correlate landscape features with Sun Bear presence, judging Sun Bears as present in an area based upon camera sightings, bait removal, or claw marks on trees. Bears were assessed as being present if they were detected once within the entire period of observation, with no finer differentiation than either present or absent, as the species is somewhat cryptic in its habits, and hard to detect. The presence or absence of Bears was then compared to seven other landscape variables; (1) elevation, (2) terrain ruggedness, (3) distance to nearest road, (4) distance to nearest permanent river, (5) distance to nearest reserve boundary, (6) human density and (7) percentage natural forest cover. The results were mapped in Quantum GIS, using elevation data from the Shuttle Radar Topography Mission, Human density data from the LandScan 2007 global population data set, road data from Google Earth Pro, combined with data obtained by mapping with a Garmin GPSmap 62s Global Positioning Unit, and other data from previous studies carried out in the area. Because Oil Palm plantations extend to the boundaries of the reserve on all sides, all areas outside the reserve were considered to have 0% natural tree cover. Statistical processing was carried out using the R software package.

Distribution of 83 remote camera stations and Sun Bear presence or absence during two remote camera surveys in Tabin Wildlife Reserve, Sabah, Malaysia, 2012–2013 (circles) and 2017 (triangles). Black circles or triangles indicate sites with Sun Bear presence, whereas white circles or triangles indicate sites with no detection of Sun Bears. Tee et al. (2021).

Tee et al. made 164 independent Sun Bear sightings over a total of 4862 study-nights, with Bears being sighted at 47 of the 83 sites included in the study. Distance from road was found to be the most reliable indicator of Human disturbance, as roads effectively run around all the boundaries of the reserve. Bears were found to be most active away from these boundary areas, with 138 of the 164 Bear-detections occurring at 35 of the 51 sites designated as 'core areas', while 26 sightings occurred at 14 of the 32 sites designated as 'boundary areas'. Thus Bears were 3.3 times more likely to be sighted in 'core areas' than 'boundary areas'. Sun Bears were most active at around 7.00 am and 4.00 pm in the core areas, whereas in the boundary areas they were most active between 5.00 am and 6.00 am. 

Predicted relative probability of sun bear presence in Tabin Wildlife Reserve, Sabah, Malaysia, based on remote camera data collected during surveys in 2012–2013 and 2017. Predictions from seven logistic regression models were multiplied by their respective AICc weights and summed to obtain model-averaged probabilities. Model covariates included distance to nearest road, elevation, human density, percent natural forest cover and survey. For models that included the survey covariate, we averaged predicted values for the two equations representing each of the two survey periods. Tee et al. (2021).

Sun Bears were found to be most present in areas away from roads, at higher elevations, and with lower percentages of natural forest cover. However, the degree of elevation present in the Tabin Wildlife Reserve is limited, with the highest parts, in the centre of the park, only reaching 571 m above sealevel, and the elevation falling to 20-100 m at the reserve's boundaries. Higher elevation was also closely correlated with terrain ruggedness, although the correlation between Bear-presence and terrain ruggedness, was much lower than that for elevation. Tee et al. suspect that the correlation between Bear-presence and elevation may actually reflect some variable not measured in their study. In particular they note that the flora of low-lying areas within the reserve is relatively uniform, but that tropical forest floras often vary considerably with even small changes in elevation, which may suggest that the Bears may be responding to the availability of some resource, such as food or cover. Bears were also found to be found in areas with lower levels of natural cover, although this measure appeared to have been skewed by the activities of Bears in the boundary areas, with those Bears detected here being predominantly detected close to the boundaries with Oil Palm plantations, 

Tee et al. had a higher detection rate for Sun Bears than previous studies carried out at other reserves in Sabah. This was particularly notable for the baited sites, but also true of the sites from the 2012-13 Rhino survey, which Tee et al. take to indicate that Sun Bears are present at higher densities in the Tabin Wildlife Reserve than in other reserves in Sabah, which in turn probably relates to the size of the reserve, which preserves a larger fragment of forest that any other reserve on Sabah, all of which are impacted by the spread of Oil Palm plantations. 

The greater activity of Sun Bears during twilight hours in boundary areas of the reserve is almost certainly an indicator of crop-raiding activities by these Bears, with previous studies having indicated that such crop-raiding is almost exclusively nocturnal, with Bears returning in the forests during the day. Bears appeared only to venture close to roads in areas where this was associated with access to Oil Palm plantations, with Bears generally avoiding roads in the interior of the reserve. 

Overall, Tee et al.'s findings are consistent with previous studies, which have found that Human activities, and in particular the spread of Oil Palm plantations, have had a strong negative impact upon the lives of Sun Bears, and that the species will tend to prioritise avoiding contact with Humans above all other activities, including foraging for food.

Studies of other Bear species have detected a similar aversion to roads, with Sloth Bears, Melursus ursinus, in Sri Lanka, having been shown to avoid areas with roads completely, and Brown Bears, Ursus arctos, avoiding roads with high traffic levels and Human settlements in general. Bears are intelligent Animals, and can modify their behaviour to accommodate Human activities, but the presence of roads is strongly associated with rises in Bear-poaching and other forms of Human-Bear conflict, which have a negative impact on Bear populations. This is of particular importance for the Tabin Wildlife Reserve, where there is no control on access from roads abutting the reserve, nor any form of anti-poaching precautions in place. Poaching in the area is known to be highly profitable, with poachers targeting both protected Animals and Plants (such as the Agarwood Tree, Aquilaria spp.). Tee et al. photographed groups of armed poachers within the reserve on three occasions, all within 1 km of a plantation road. 

Malaysia is the world's second largest producer of Palm Oil, and Sabah produces about 27% of the country's total output. Unsurprisingly, Sabah is also a global deforestation hotspot, with 15 000 km² of Oil Palm plantations, out of a total land area of 74 000 km². This expansion of Oil Palm plantations has been accompanied by an expansion of the infrastructure which supports such activities, most notably roads. In an area such as the Tabin Wildlife Reserve, which is surrounded by plantations and roads on almost all sides, simple passive protection of species such as Sun Bears (i.e. declaring these species to be protected and hoping people will comply with this) is unlikely to be effective, and a more robust species protection plan will need to be put into place if these Animals are not to go extinct. Any such species protection plan needs to be built upon studies of hunting and poaching in the area, and the responses of Bears to Human activities, and include rigorous anti-poaching measures and formal partnerships between locally-based non-governmental organisations, local ecotourism resorts, plantation stakeholders and local communities.

See also...

Follow Sciency Thoughts on Facebook.

Follow Sciency Thoughts on Twitter.